Transport system for single sheets of photosensitive material



April 8, 1969 G. ENKE ET AL 3,437,336

TRANSPORT SYSTEM FOR SINGLE SHEETS OF PHOTOSENSITIVE MATERIAL Filed Feb.8, 1967 United States Patent 3,437,336 TRANSPORT SYSTEM FOR SINGLESHEETS 0F PHOTOSENSITIVE MATERIAL Gerhard Enke and Heinz Isermann,Siegen, Germany, as-

signors to Meteor-Siegen Apparatebau Paul Schmeck 'G.m.b.H., Siegen,Germany, a corporation of Germany Filed Feb. 8, 1967, Ser. No. 614,740Claims priority, application Germany, Apr. 28, 1966, M 69,327 Int. Cl.B65h 5/02 US. Cl. 271-45 5 Claims ABSTRACT OF THE DISCLOSURE A conveyorbelt transporting apparatus for photosensitive sheet material, whichbelt attracts the sheets electrostatically, the electrostatic chargebeing applied to the belt by a potential carrying metal strip whichextends transversely of the belt and contacts its underside, thusallllovging for controlled application of electric charge onto t e elt.

The invention relates to a system for transporting single sheets ofphotosensitive material in a given plane, more particularly xerographicor photographic copying material into and out of the exposure positionin the focal plane of the copying machine.

Such a system has been proposed comprising an endless conveyor beltwhich is tensioned between drive and reversal rollers, consists ofelectrostatically chargeable material, and the operative run of whichhas its underside sliding over a plate in the region of the said givenplane, an electrostatic charge being transmitted to the conveyor belt tocause the transported sheet to be attracted to said belt.

The advantage of such a system is that the sheet which is to betransported is not subjected to any suction forces of the kind which areexerted substantially nonuniformly in known vacuum-chamber transportsystems. The vacuum-producing means required with the latter type ofsystem also making the same expensive. The electrostatic attraction ofthe sheet to the conveyor belt eliminates the need for edge clampingmeans and also ensures that each single sheet occupies a perfectly fiatposition, this of course being important in the exposure ofphotosensitive material.

In a particular such proposed electrostatic attraction system, the plateintended to ensure that the conveyor belt and hence the sheet retainedthereon move in a given plane, and the conveyor belt itself, consist ofmaterial which is a poor electrical conductor, e.g. a plastic material,so that the electrostatic charge required to attract the transportedsheet is produced directly by the friction of the conveyor belt on theplate during the transport movement. Although this arrangement has theadvantage of a simple construction, it has been found a disadvantagethat the static electricity is not constant so that incorrect transportfrequently occurs, the sheet occupying a crooked position on theconveyor belt. This may, for example, be owing to the fact that thecharge produced by friction is greatly dependent upon the relativehumidity, and the charging process is also dependent upon the timeduring which the apparatus has been in operation. At the start ofoperation, e.g. after the copier containing the system has been switchedon, the static electricity is frequently inadequate to ensure reliabletransport, whereas after a relatively long period of operation theelectrostatic charge is frequently so great that not only does the3,437,336 Patented Apr. 8, 1969 sheet adhere to the belt, but after acertain standstill time the belt will tend to adhere to the plasticsplate.

To obviate this disadvantage and render the transport system independentof static electricity, according to the invention, a metal stripextending transversely of the direction of movement of the belt isprovided in front of that edge of the plate on to which the conveyorbelt runs, and means are provided for applying a DC. voltage of highpotential with respect to earth to said strip. In this way the conveyorbelt always has the charge suitable for the transport of a particularcopying medium. Moreover, this state of charge exists where it isrequired to ensure satisfactory transport.

In the system according to the invention the plate need not necessarilyconsist of an electrostatically chargeable material, e.g. a plasticsmaterial, but it must not discharge the charge transmitted to theconveyor belt. If a plastics plate or the like is used for this reason,its surface in contact with the underside of the operative run of theconveyor belt is roughened to ensure that there cannot be any additionalcharge due to friction and no electrostatic adhesion.

It has been found very advantageous to form the metal strip from a foilwhich engages around the plate end side adjacent the oncoming conveyorbelt, or a wire disposed at or near said end edge. An arrangement ofthis kind will be used when the photosensitive sheet has beentransported only through the exposure position, i.e. in just one planeand over just a relatively short distance. If transport is over a longerdistance and possibly a deflected path, the metal strip supplying theelectrostatic charge may be disposed separately of the plate, and moreparticularly at a place where the sheet is passed to the conveyor belt.

In xerographic copiers the DC. voltage fed to the metal strip will bederived preferably from the corona discharge voltage. This obviates theneed for a separate charging unit.

In order that the invention may be well understood there will now bedescribed one embodiment thereof, given by Way of example only,reference being made to the accompanying drawing, in which:

FIGURE 1 is a side view of a sheet transport embodying the invention;and

FIGURE 2 is a plan view of the same system.

A conveyor belt 5, consisting for example of tetrafiuoro-ethylene(trademark Tefion) runs over a reversing roller 1 and a drive roller 2.An electric motor 6 operably connected to a bevel gear 7 drives thedrive roller 2 in the direction of the arrow shown in FIG- URE 1.

The top operative run of the conveyor belt 15 runs over a plate 3, ofwhich the edge adjacent the conveyor belt in contact therewith isenclosed in a strip of metal foil 4. This strip is electricallyconnected to the charging unit 8, which is indicated diagrammaticallyand which delivers a relatively high DC. voltage. When the system isused in a xerographic copier, the charging unit may be the charging unitprovided in the copier to produce the corona discharge. The rollers 1and 2 (and the charging unit 8) are advantageously earthed.

What we claim is:

1. In a system for electrostatically adhering a sheet of photosensitivematerial to a bight of an endless conveyor belt made ofelectrostatically chargeable material, drive and reversal rollers forsaid conveyor belt, a stationary support plate, means for driving saiddrive roller in one rotary direction to move said bight in contact withone face of said plate from one edge to an opposite edge of 3 the plate,a metal strip extending transversely of the direction of movement ofsaid bight at said one edge of the plate, and means for applying to saidmetal strip a D.C. current of high potential with respect to ground.

2. A system as set forth in claim 1, in which said metal strip comprisesa foil folded about said one edge of said plate.

3. A system as set forth in claim 1, in which said metal strip comprisesa metal wire.

4. A system as set forth in claim 1 for a xerographic copier, in whichsaid D.C. voltage is derived from the corona discharge voltage.

5. A system as set forth in claim 1, in which said drive and reversalrollers are grounded.

RICHARD 4 References Cited UNITED Levine 226-94 E. AEGERTER, PrimaryExaminer.

US. Cl. X.R.

